1. Field of the Invention
The present invention relates to a camera flash module, and more particularly, to a camera flash module that may adjust a direction of a light so as to match an angle of view of a camera.
2. Description of the Related Art
As digital cameras have been popular, various mobile communication terminals containing a built-in small-digital camera have been manufactured and provided in the market.
Digital cameras, built-in cameras of mobile terminals, and the like may contain a flash that provides an amount of light required for photographing images at night. A camera flash module is contained in most mobile communication terminals that are currently produced, so that users may clearly photograph images at night.
At least one light emitting device is mounted on a printed circuit board (PCB) surface, in the camera flash module, so that a light source emits a light to an external side through a condensing lens set on a mobile terminal, and the at least one light emitting device may emit a light using power supplied from the mobile terminal. Recently, a light emitting diode (LED) has drawn attention for use as a flash light source.
To effectively utilize a light emitting device in the camera flash module, the camera flash module needs to adjust a light to match an angle of view of a camera, in addition to simply emitting a light. Due to a characteristic of a camera, there is a difference between a range of a light emitted from a light emitting device and a range of a light required by the camera and thus, the range of light emitted by the light emitting device may be adjusted through a lens.
Since an illumination angle of the light emitting device is greater than an angle of view of a camera, when only the light emitting device is used, a ratio of an incident light in a photograph area of the camera to a light emitted from the light emitting device is significantly small, and a light efficiency decreases. Therefore, a plurality of lenses is included on a foreside of the light emitting device.
When a Fresnel lens that minimizes a size of a lens is used, a light emitted from a light emitting device may be difficult to be controlled and thus, a light efficiency may decrease. Also, when a lens is provided in a circular shape, a light passing through the lens is emitted in a circular shape and thus, the light emitted in a circular shape may not be optimized for the photograph area of the camera which is provided in a quadrangular shape. Accordingly, a light loss may significantly occur.
Accordingly, many lights are out of the photograph area of the camera and thus, a light efficiency may be low. Also, little light is illuminated to a corner of the camera and thus, a brightness uniformity may decrease and a quality of an image may decrease.
Therefore, to effectively utilize a light emitted from the light emitting device, a lens included in the camera flash module may include a refraction unit to control a light from the foreside of the light emitting device and a total reflection unit to effectively use a light from a side of the light emitting device.
A current light emitting device flash lens may be classified into two groups: a light emitting flash lens having a circular side total reflection unit and a light emitting flash lens having a quadrangular side total reflection. Even though the circular side total reflection unit may be readily manufactured, a performance may be deteriorated since a size of a screen of a camera has a width to height ratio of 4:3, which is the characteristic of cameras. Even through the quadrangular side total reflection unit may be difficult to be manufactured, the quadrangular side total reflection unit may be manufactured to fit the size of the screen of the camera. Also, an amount of illuminance in a required area is greater than the circular side total reflection and thus, the quadrangular side total reflection unit is preferred.
A ratio of an ambient light to a central illuminance at 1 meter (m) away from the light emitting flash may be important and the ratio may be referred to as a brightness ratio or a light intensity uniformity. When a center is significantly bright and an ambient is significantly dark, edges of a photographed image may be developed to be dark and thus, the ratio of the ambient light to the central illuminance needs to be greater than or equal to 60%.
The light emitting device flash lens may be classified into two types: an integrated type including a light emitting device and a lens as one package and a separable type including a light emitting device and a lens which are separable from each other.
In the integrated type, a light emitting device and a lens are packaged as one and thus, a degree of distortion in a tilt and an optical axis between the light emitting device and the lens is significantly low. However, an additional window is included in the mobile terminal and thus, corresponding components may also be added.
In the separable type, a lens is formed on a window surface as a Fresnel lens type so that the window of the mobile terminal may provide a function of a lens and thus, a number of components used in the separable type may decrease when compared to the integrated type. However, a distance between a light emitting device and the lens is significantly greater than the integrated type and thus, energy loss may occur. Also, a degree of distortion in a tilt and an optical axis between the light emitting device and the window lens is high and thus, an assembly error rate may increase.
Demand from the market for a flash that is readily managed and provides a great amount of light for a high-resolution camera is high and thus, the integrated type is preferred. However, the integrated flash lens has a drawback in its manufacturing process. A distance between a light emitting device and a lens may need to be constant so that a light emitted to an area that requires light may satisfy the requirement. However, a camera flash module lens is made from silicon that is robust against heat and has a low strength and thus, assembly of the light emitting device and the lens may be difficult and maintaining of the distance between the light emitting device and the lens to be constant may also be difficult. Therefore, there is a desire for a camera flash module having a structure that does not need to maintain the distance to be constant.